Hansen Bruce C, Essock Edward A, Zheng Yufeng, DeFord J Kevin
Department of Psychological and Brain Sciences, University of Louisville, Louisville, KY 40292, USA.
Network. 2003 Aug;14(3):501-26.
The amplitude spectra of natural scenes are typically biased in terms of the amount of content at the cardinal orientations relative to the oblique orientations. This anisotropic distribution has been related to the 'oblique effect' (the greater visual sensitivity for simple line/grating stimuli at cardinal compared to oblique orientations). However, we have recently shown that with complex visual stimuli possessing broadband spatial content (i.e. random phase noise patterns), sensitivity for detecting oriented manipulations of amplitude is best for oblique orientations, and worst for horizontal orientations (the 'horizontal effect'). Here we investigated this effect with respect to the phase spectra of natural scenes. Oriented manipulations of both amplitude and phase were made on a set of natural scene images that were dominated by naturally occurring structure at one of four orientations in order to determine whether the presence of predominant scene content, carried by the Fourier phase spectra, altered the ability to detect an oriented increment of amplitude. The horizontal effect was observed regardless of any scene's content bias. In addition, a content-dependent effect was observed which could be related to the presence of spatial structure conveyed by the phase spectra of this set of natural scenes. Results are evaluated in the context of a divisive normalization model.
自然场景的幅度谱通常在相对于倾斜方向的主要方向上的内容量方面存在偏差。这种各向异性分布与“倾斜效应”（与倾斜方向相比，在主要方向上对简单线条/光栅刺激具有更高的视觉敏感性）有关。然而，我们最近表明，对于具有宽带空间内容的复杂视觉刺激（即随机相位噪声模式），检测幅度定向操纵的敏感性在倾斜方向上最佳，而在水平方向上最差（“水平效应”）。在这里，我们针对自然场景的相位谱研究了这种效应。对一组自然场景图像进行幅度和相位的定向操纵，这些图像在四个方向之一上以自然存在的结构为主，以确定由傅里叶相位谱携带的主要场景内容的存在是否会改变检测幅度定向增量的能力。无论任何场景的内容偏差如何，都观察到了水平效应。此外，还观察到了一种与内容相关的效应，这可能与这组自然场景的相位谱所传达的空间结构的存在有关。结果在归一化除法模型的背景下进行评估。
